Radio bomb release system



Dec. 23, 1947.

Filed Oct. 2, 1944 3 Sheets-Sheet 1 .5M/TWIN 60A/TML DEM/Kt' m E `N Afm m@ f Y llm yf.. .5 n. 1H/4; ,w L d DTNCE Dec. 23, 1947.` D. G. c. LUCK RADIO BOMB RELEASE SYSTEM )Filed oct. 2, i944 5 Sheets-Sheet 2 DEV/CE L- L s INVEN TOR.

Dec. 23, 1947. D. G. c. LUCK 2,433,284

I v l RADO BOMB RELEASE SYSTEM Filed oct. 2., 1944 s sheets-sheet s i i. Q QEUMINOR. G I l BY" N Patented Dem-23, 194'? UNITED STATES OFFICE natia G. o. Luck. Princeton, N. J.; assigner-itt Radio Cox-poration of Anerica'-,` a corporation of Delaware' ji-nie iiiverittowei 'tes to radio point release systems and 'more Yparticularly to improvements in systems of the tinteA from target computing type, Vsuch as those descritte-1 in p'aterit Number 2,415,223 issued to Royuen C'. senders, J'r'.. on February 13, .1947, an'd in operding U. s. patent application ser. No; 547,203 med J`u1`y29', 1944;, by Royden C.A"S4ander s Jr., and `entitled Aircraft navigation.V As descibedin more detail hereinafter sucrisyst'emsoperat by making substarif tney eontinuoue measurements of the distance; of aselected v target andthesped of the bomber Withwrespectto said target. computing the pre-'- noted time from target inl response to seid meas: urements. At a predetermined time from target, depending upbri'tne altitude and speed of trie bomber craft, a bomb is released.

Many systeniyiiich measures the distance and speed of a mobile craft with respect to a target by virtue of r'ad waves reflected frornfsaid tar; get will respond to the true distance and the radial component of speed, rather than the horizontal distance, that is Vtl'ie dis'tance measured in a plane parallel' to the surface, and the ground speed. As long as the distance of the bomber from its 4target is relatively 'great with respect to the altitude, the true, or slant, distance is substantially Vequal to the horizontal distance, and the slant speed of the bomber with respect to its target is substantially equal to the hriL zontal, o r groundspeed. However, asthe bomber approaches a point directly over the target, these relationships no lnger Vhold true and the' time from target predicted on a ground range and ground speed basis from 'adi'o measurements' of slant distance and slantV speed will not approxiL mate the actual time period which will beV re"`= Y quired for the bomber to reach the point over the target with sufficient accuracy.

Ink the systems described in the above-meri: tioned copending applications, the error resulting from the measurementnof slant vspeed and distance rather than horizontal speed and dis-" tance are allowed for 1inthe adjustment of release time. This allowance must be determined iii accoifdanc'eh with the speed and altitude ef the bomber, and be adidfto 'trie time or fairer tje" bont, widower leva nicht is funetion of suo-V stantially only 'the altitde. n n Y n cussin is based onv the' a ssiiinptionl that the' bomber approaches the target in level night.V

VIt is the principal object of the present invention to provide ififeans for automatically releas: ing a bomb.

. operation of the systemrof `Figure 5.

Referring to Figure 1,l la distance measuring device l is arranged to provide an output voltage having a magnitude proportional to the distance of the target or objective from a fait (not shown) carrying the eduipment. The device l may comprise radio reflection equipment, similar to'V that used in the well known Yfrequency modu-V lation type of `altimeter, or any other known means Vfor providing the required distance-pro'h portional output. The distance measuring de; vice I is provided With a sensitivity control 3, which may be merely an adjustable attenuator, or may be any other means for controlling the proportionality oiqthe output to distance.

A speed measuring device 5, which may also be of the radio reflectib'rtype, is arranged to provide an output voltage 'proportional to the speed or the mobile craft tiitr spt t Vtlie ob'jetiv'. The output circuits of the speed and distance measuring devices 5 and I are connected to a relay circuit 1, in such'manner that the Vtwo outputs oppose each `other relayY circuit 'Lis lly operated ntt means; electron dihare tube means, or both, in accordance with known and conventional practice. The relay circuit 'I is adjusted so that when the polarity of the input thereto is similar to that of the output of the distance measuring device I, the motor 9 is energized to run clockwise, for example. When the polarity of the input to the relay circuit 'I is similar to that of the output of the speed measuring device 5, the motor 9 is energized to run counter-clockwise.

The shaft of the motor 9 is mechanically coupled, as indicated schematically by the dash line I3, to the sensitivity control 3. An indicator I5, provided with a scale I'I, is similarly coupled to the motor 9. The scale I'I may be calibrated in units of time, such as seconds.

In the operation of the above-described system, the distance measuring device I produces an output voltage ed=aR where R is the distance and a is a constant determined by the design of the device I. The speed measuring device produces an output voltage v=bS where S is the velocity and b is a constant determined by the design of the device 5.

The sensitivity control 3 changes the voltage ed by a factor r, providing a voltage where the value of r is a predetermined function of the mechanical setting, or angular position of the control shaft of the sensitivity control 3.

The voltages ed and ev are applied, in opposition to each other, to the relay circuit 'I. The resultant input to the relay circuit is thus As long as e0 is not equal to zero, the motor 9 will be energized to drive the shaft in the proper direction to reduce the dierence between the speed and distance components of the voltage en,

by varying the ratio r. The value of e0 will be substantially continuously maintained at zero by this operation, and

raR=bS Factoring and transposing: EIL S-ra The quantity is the distance of the objective divided by the speed with respect thereto, Subject to the condition that the motion is such as to decrease, rather than increase the distance R,

Where T is the time from target. Thus where lc is a constant and equal to tation, or as an alternative, the mechanical connection I3 may include variable ratio gearing or cam means arranged in known manner to provide reciprocal variation of r as a function of input shaft rotation. However obtained, this reciprocal characteristic need only extend over the range of time T required by the application of the equipment, i. e., not necessarily from Tr() to T=. The indicator I5 will assume, within the limits of the operating range, an angular position which is a predetermined linear function of T, providing direct indication upon the scale I'I. The shaft of the motor 9 may be coupled also to any other device to be controlled in accordance with the time from target, T, such as a bomb release mechanism, not shown.

It will be apparent that a linear relationship between T and r may be obtained also by controlling the response of the speed measuring device, rather than that of the distance measuring device, This arrangement is not illustrated in the drawing, since it involves merely the transfer of the control 3 from the output of the device I to that of the device 5, and modification of the control 3 to provide linear variation of sensitivity with T. The operation of the system as thus modified is identical with the operation of the system of Figure 1.

As mentioned above, the system of Figure 1 will provide correct indication of the time required for the bomber to reach a point directly above the target only under the condition that the altitude be negligible with respect to the distance. Referring to Figure 2, assume that a bomber, at present at the point P, is flying horizontally with a velocity G, at an altitude H, toward the point M, directly above a selected target situated at a point Q. The time which will be required for the bomber to reach the point M is the horizontal distance divided by the horizontal speed:

The quantities D and G, however, are not those measured by the devices I and 5, The distance measuring device I measures the slant range R, which is greater than the distance D, and the speed measuring device 5 measures the slant speed S, which is less than the horizontal speed G. R/S is not equal to the true time from target D/G, but diiers from it by an amount which increases as the bomber approaches the point M. At this point, the measured distance R is equal to H and the measured speed S is zero, R/S indicating infinite time from target rather than zero.

Referring to Figure 3, assume temporarily that H=0 so that R and S are equal respectively to D and G. Then at some specied time from target To, the relationship between R and S is represented by the straight full line R0, For any given value of distance R, there is a particular speed S which is required in order for the bomber to reach the target within a time To. In other words, the slope of the line Ro is:

When there is an altitude H to be considered, the situation is illustrated by the solid curve R of Figure 3. Bearing in mind that the curve illustrates conditions pertaining only to a single specified time from target To, the curve R shows the relationship between slant speed and slant distance associated with the value To of true time from target. The indicated time from target, representing R/S, varies with the slant speed S and is equal to theslope of the line R", extend- 5. ing from .the orig-in to the .point on the .curve R corresponding .to the 4speed S. .At .relatively high values .of S or relatively .long range, lthe' curves ,IR and R" approach asymptotically .the curve R0. Ont-he other hand, at low speedsand high altitudes, Lthe slop :of vthe line R" .departs materially from that of the line R0, resulting in serious `errors in the -determination of time from target by the system -of Figure l.

As a practical matter, the bomb -release system will be required to operate accurately only throughout a predetermined .range of values of slant .speed S. Referring to Figure 3, the upper and lower limits of this speed range are indicated as S and S". The curve .Ramay be approximated very closely throughout `-this .range .by the straightline R/having a slope T somewhat .less than the true time from .target To, and intercepting the axis of abscissaeatadistance SQ from 'the origin. The 4equation 'of this .linear approximation is As -will be shown the proper use of Jthe approximation represented lby the iline R' permits 'mec'hanical determination of fthe true time from target To to a high degree fof Aaccuracy throughout the ranges of altitude fandspeedusefulin .low altitude bombing.

In laccordance with the present invention, it :is I

proposed to modifylthe `systemf'of Figure l1 to operate upon a linear approximation such .as 'that illustrated by the line Ri of Figure 3. This done by superimpos'ing upon the sensitivity control 3 a correction to compensate for the ldifference in slope of the 'line AR' -'from that of the line Rp, and providing in=addition tothe output ofthe speed measuring -device i5 a `correctionbias yin ace cordance with vthe `.intercept distance Se of .the

line R. Ithasvbeeniound that both of said corf where g is the gravitational acceleration, 32 feet per second, and Tf .is the 'time of fall. Release must occur when 'time from target 'equals' time VAof fall, .so that atrelease and the condition Iwhich must Yproduce :release iis Referring to vFigure A4, wherein elements lsimilar to those of the system of Figure 1 are indicated by correspondingreference numerals, vasen- .sitivity correction control device I9-'is connected in cascade with'thesensitivity control .3 between the control 3 and the input to therelay .circuit V1..

V The sensitivitycontrol 'device .I9 may be similar to the control 3, and operates merely nto .super-s impose upon the veffect .of `the control 3 another. and considerably smaller variationlof sensitivity.v

A D.C. Ysource 2| is also coupled through a voltage control device 23 to the input circuitcf the relay 1, in series with the outputs of `the sensitivity correction control I9 and the .Speed measuring device 5. The device 23 may be a Voltagedi vider of any known type.

An altimeter 2,5, which may be of the F-M ra.-l dio reflection type, but is 4in any c ase arranged to provide an output Voltage proportional to valtitude, is connected to a .relay circuit .21. The relay circuit 21 may be identical with the .relay circuit 1. The D.C. source 2| is connected through two cascaded voltage control devices 29 and 3| to the relay circuit 2-1 in series with the altimeter 25. The control'devices29 and -3I are similar to the control 23, :and are so designed vas to prevent interaction due gto loading of the confA trol 29 bythe control 3l.

The relay circuit 21 is connected to a power source 33 and a reversible motor 35. The connec tions and the operation .of the relay 2.1 .andthe motor 35 are similar to those of the relay 1 and the motor 9.

The motor 35 is mechanically connected to:an indicator 31 provided with a scale 39, which may be calibrated in terms of H /T. The motor 35 is also coupled as indicated by thedash lines 4I 43, to the voltage control devices 23 and 3,! .and .to the sensitivity correction control device I9. The motor 9 is coupled to the sensitivity control 3 as'. in the system of Figure 1, and is also coupled Vto the voltage control 29,as indicated by the dash line 45.

A comparison device 41 is coupled to the motors 9 and 35. The device .41 .includes means irresponsive `to the angular positionsof Ythe .shafts iojf thezmotors 9 and 3.5 to close a circuit upon the at-` tainment .of a predetermined relationship therebetween, as set'forth more fully below. The .dee vice 41 isv electrically `connected to a bomb ref lease mechanism, not shown.

In the operation of the system Vof Figure .4,'the ydistance lmeasuring device provides an output dR, as in the system of Figure 1. Similarly, the speed measuring Vdevice provides lan output bS. The D.C. source 2| provides a .constant voltage c. As in the system of Figure 1, the sensitivity con.- trol 3 modifies the output of the distance measuring device I by a factor r, so that the output of the device 3 is raR.- This voltage .is further modified by a factor u by the correction control device I9, providing an .output therefrom uraR. The factor u, as will appear hereinafter, ls a quantity relating the slope of the linear `approximation of Figure 3 to the true time from target. The voltage control 23 modifies the .output .c .of the D. -C. source 2I by a factor p, providing 1a a voltage pc. The voltage pc corresponds to the intercept S0 of Figure 3. The total input .to .the relay circuit 1 is:

Assuming that the controls I9 and 23 remain-ad.- justed correctly, the relay circuit 1 will vlenergize l the motor 9 as in the system of Figure v1 -to drive provided by the control I9 and the intercept bias p provided by the control 3 are both functions of H/T. Accordingly, the output shaft of the motor 35 is continuously maintained at an angular poition corresponding to the quantity H/T as folows:

The voltage control 29 modifies the voltage c derived from the source 2| by a factor m providing an output voltage mc. The voltage mc is further modified by the control 3| by the factor q providing a voltage qmc. The voltage qmc is applied to the relay 21 in opposition to the output nH of the altimeter 25. The relay circuit `21,controls the motor 35 to drive the voltage control 3| to a position such that the total input to the relay 21 is zero, whereupon This operation takes place concurrently with the above-described operation of the motor 9. Upon the attainment of equilibrium conditions, the factor m will be proportional to the time T:

(2) m=fT Substituting in Equation 1 (3) nH-qfTcr-O and Since f, c and n are constant, Equation 4 may be rewritten as Where Since the factor q is proportional to the angular displacement of the motor 35, the operation of the system is seen to constrain this displacement to be proportional to H/ T. Thus the correction control |9 and the voltage control 23 are positioned by the motor 35 in accordance with the magnitude of the quantity H/ T, and within the limitations of the approximation of Figure 3, the shaft of the motor 9 assumes an angular position closely approximating the true time from target. into consideration the various constants of the The comparison device 41 is adjusted, taking into consideration the various constants of the system, to operate upon the attainment of the relationship between the shafts of the motors 9 and 35 corresponding to the condition that 2 H "y TT In practical application of the invention, it has been found desirable to combine the functions of distance measuring and speed measuring in a single system to provide time from target information without the intermediate steps of independently measuring the speed and distance. Also a memory system similar to that described in U. S. patent Number 2,416,223 may be included, to enable accurate operation notwithstanding momentary failure of the radio reflection signals.

Referring to Figure 5, a radio transmitter 5| is connected to an antenna 53 and to a frequency modulator 55. The modulator 55 may be of the vibratory variable capacitor type such as that described in copending application Ser. No. 471,- 003 led January 1, 1943, by S. V. Perry and entitled Capacity modulator unit, or any other 8. known device for varying the frequency of the transmitter 5| in response to a modulating voltage. The input circuit of the modulator 55 is connected through a manually adjustable voltage divider 49 to a wave shaping circuit 51 which is connected through a voltage divider, |9, a series rheostat 3 and a resistor 55 to a square Wave generator 63. The rheostat 3 has a linear resistance-rotation characteristic. Since the output of the square Wave generator 63 is of constant amplitude, the current through the resistor 65 and the voltage divider I9 is inversely proportional of the angular position of the movable contact of the rheostat 3.

A receiving antenna 61, similar in construction to the antenna 53 is connected toa receiver 69. The transmitter 5I is also connected to the receiver 69 through a line 1|. Both antennas 53 and 61 are preferably directive, and are arranged to provide maximum response in the same direction.

The output circuit of the receiver 69 is connected to an amplifier 13. Theoutput circuit of the amplifier 13 is connected to an amplitude limiter 8|. The output circuit of the limiter 8| is connected to a switched pair of averaging cycle counter circuits, generally designated by the reference numerals 83 and 85 respectively.

The counters 83 and 85 are provided with a common load resistor 81 which is connected to the control grid of an amplifier tube 89. The anode of the tube 89 is connected directly to a D.C. source 9|. The cathode circuit of the tube 89 includes a resistor 93 tapped at an intermediate point 94. The cathode of the tube 89 is connected to the control grid of a tube 95. The anode circuit of the tube 95 includes one winding of a differential relay 91. The other winding of the relay 91 is connected in the anode circuit of a tube 99. Anode potential is applied to the tubes 91 and 99 by the source 9|. The cathodes of the tubes 95 and 99 are connected to ground through a common resistor IUI.

The counter 83 includes a capacitor |93 connected to the cathode of a diode |95 and to the anode of a triode |91. The cathode of the tube |91 is connected to theload resistor 81. The con.. trol grid of the tube |91'is connected to the square wave generator 63. The anode of the diode |95 is connected to the cathode circuit of the tube 89 at the point 94 on4 the resistor 93. The counter comprises-a capacitor |99 connected to the cathode of a diodeV I| and to the anode of a triode ||3. The anode of the diode ||I is connected to the load resistor 81. The cathode of the triode ||3 is Aconnected to the cathode of the tube 89. The control grid of the tube ||3 is connected to the outputcircuit of a phase inverter H3, which is connected to the square wave generator 93. The lower end of the load resistor 81 is connected to the adjustable tap of a voltage divider ||5, which is connected in series With fixed resistors ||1, 9 and |2| and a second voltage divider 23, across the source 9|. The adjustable tap ofthe voltage divider 23 is connected to the control grid of the tube 99.

The output circuit ofthe amplier 13 is connected to a rectifier 15. The output of the rectifier 15 is applied to a D.C. amplifier 11, which is connected to a relay 19. The amplifier 11 is biased so that the relay 19 is open in the absence of output from the amplier 13, and is closed when the output of the amplifier 13 exceeds a preldetermined value.

Ehe relay 1.BE'I is proVided-With-:a double-throw idouble-pole :contact arrangement .connecting a Abattery -II ttofthefarmaturefcircuit of a reversible anotor -9 iso fthan when the relay armature is -in one position -the motor y9 is Aenergized to .run in Aone directionfand `when ythe :relay armature isin fits other fposition, :the `:motor 9 is energized to a-un 'in the opposite direction. This circuit `also .includes thefcontactsoftherelay 'I9-so thatii'the received :signal tails, the tmotor .9 .is deenergized. The operation of thesy-stern Vthus Yfar described fis as follows: The'square -wave voltage output of .the generator 63 is attenuated to Y-an extent -de- ,pending upon the .positions-ortheadjustable taps of the ,resistor 3 andthe voltage divider I-EI, and :appliedtofthe wavei-sh-apingcircuit='I. The Wave ishapingfcircuit 5 1 includes a lter .or @other lmeans ,for modifying the fsquare lWave `input fto produce Iaan output of rwave lshape suitable for driving the {modulatorf soas to cause triangular :Wave variation of frequency of `zthe rtransmitte'r I. The out- ;put oftthe wave shapingftcirouit 51 is lturther at- :tenuated by the .voltage adivided A9 fand applied ao the :modulator Slhe .frequency modulated signal produced by the transmitter 5I is radiated `fby the antenna '.itotheftargetfnot shown. :Part roi vtheeneligy strikingithestarget isreected to "the receiving antenna B1. The received reectedLsigfri-a1 is combined fintthe receiver 69 with some of the -original `frequency mo'dulated signal, ,which 30 is .conducted vdirectly tfrom Athe ntransmitter 'to the receiver 69 through thejline 1I. The output `of the -receiver 69 =includes a beat :signal having a frequency equal -to the difference between-tiredn- :stantaneous frequencies :of the transmitted and freceivedfsignals. `-The-beatzoutputof the receiver 69 is ampliiied by the amplier s1131andslimited'to5a :constantampgitude by the ylimiter '81. The output -of `the 'limiter :BI is asquare wave 'voltage .having -a frequency .fequal ato Athe idiference .'betwe'en the frequencies of =the transmitted :and received Asig- :nals and `a :constant amplitude Es.

Referring -to Figure t6, "the frequency fof :the itransmittedsignal .is represented bythe :solid line 113. This frequency waries uniformly .throughout the modulation cyclein response to fthe triangular wave 'output of the Wave shaping circuit 51, between upper and lower limits f'ziandffl, refspectively, about ga mean value rfo. The sweep width fz-f1 is proportional :tothe amplitude of the triangular Wave input to `the .modulator `55, and.hen`ce 'is a function ofthe position 'of l"the iadjustable contacts :of the yoltage dividers 449 `and I9, :and 'the vtrheostat 3. Assuming that v`there is zno relative imction between Athe bomber @and the itarge't, fthe reflected :signal is 'delayed with -re- .spectto 'the transmitted signal `by the time re- .:quired :for the .radiation #to travel trom the 'transvmitting Vantenna 53 -to the target, fandback -to the ireceiving antenna 61. This 1is 'indicated bythe -dotted line 1.I=.'i5 inFigureiZ. 'Therelected Vsignal variesin trequencyfover the y'same range z-fi 'as Vfthe transmitted "signal, 'but constantly difers in `Efrequency from :the transmitted signal by an `amountproportionalito the distance. This diterence tin -requen cyrlis 'Wft'li :where yl7f==f2-j1 .in .megacycles 1per esecond,V fmfis 'the modulation frequency in cycles pertsecond, -,or.fr.equenoy of operationof:thesquarefwave'gen- .erator 13, $.84 lis .the `velccity-.of .wave prt pagation in feet .Per linicrcsec'ondand is the distance-.Jin et. If equipmentlis .moving toward `,the

= cynlesfperssecnnrl .targets the received signal .-is .increased in fre- ;quency, owing to Dopplereffect, .by an 'amount :Where :S is the velocity in feet per second, 'fo lis the .carrier frequency in megacycles per second 'and 98.4 is the'velocity of radiation propagation in :feet .per microsecond. The frequency of the received 'signal with relative motion is represented by lthe dash .line I'II in VFigure 2. This frequency .varies `throughout'the modulation cycle :over xa Afrequency :band which is equal in width toithat di "-.the transmitted signal. The diierence in .frequency between .the transmitted and received signal is -Wfm'R 2Sf0 cycles per second during increase in frequency o'f the transmitted signal, and

;Zfr fd 984 984 cycles per second -during decreasein frequency of the transmitted signal.

The constant-amplitudebeat frequency output of the limiter 8l is appliedto both of the counters 83 and 85. During the modulation upsweep, or increase in -frequencyof the transmitted signal, the square wave generator 6'3 applies a positive :pulse to the control grid of the Vtriode `IilI and .to -lthe Fphase inverter H4, as indicated by `the graph of Figure '7. The phase inverter providesa .negative pulse whichis applied to the control grid ,of the .triode -II3 -of Vthe counter 85, as indicated bytl'ieg-raph ofFigure 8. The triode I I3 is thereby Iout ou, and the counter `85 prevented from operating. ,The triode rIIl'I isconductive, allowing the capacitor IUS to charge :through the resistor 81 duringpositive half cycles of the'output of the limiter 8I'. During negative half cycles of the limiter output, the capacitor |03 is discharged through the'diode .H15 to the potential appearing .at :the tap 9A .of the resistor .93, which is slightly .'less than 'thepotential at the cathode of the tube '89 4Landhence the cathode of .the tube IGI. The -yalues of `the capacitor i113 land resistor B'I are suchthat the capacitor :I D3 becomes substantially lfully :charged to the limiter output voltage Es .during each cycle 'of the limiter output. Thus during the modulation upsweep, the counter B3 causes .raicurrent iu toflowydownward through the .resistenti-Las .indicated by the solid arrow. This .current is proportional to the Y:product of the charge deposited in thecapacitor ID3 during each `cycle, and thenumber of v,cycles per second:

-wheref islth'e .beatifrequencm 'Q is the-charge per 'cycle, .C i is 'the .capacitance of the capacitor |03, fand .Es .is the Aamplitude `nf the output of the limiter 8l. Since 'rw Uff '984 41mm fztsuu 984 During the .modulation downsweep, vthe square Wave generator E53 provides a .negative pulse -at the-gridof the triode H31 andthe phase inverter ..I-I,.and.a positive pulse at the grid of the triode .15 .'-I-I3., as indicated by .the portions I'IS :and ;I8I, re-

spectively, of the graphs of Figures 7 and 8. The counter 83 is now inoperative and the triode ||3 is conductive. During negative half cycles of the limiter output, the capacitor |99 is charged through the diode I I I and the resistor 91. During positive half cycles, the capacitor I 99 is discharged through the trode ||3 to the potential existing at the cathode of the tube 89, which is substantially equal to that at the anode of the diode I I I. Thus during the modulation downsweep, the counter 85 causes an average current is to flow upward through the resistor 81 as indicated by the dash arrow. This current is proportional to the product of the charge deposited in the capacitor |99 during each cycle, and the number of cycles per second:

where C2 is the capacitance of the capacitor |99. Since The average current through the resistor 81 is o=uid Refer to Figure 9, wherein I1 is the average component of current during upsweep due to distance, I2 is the average component of current during downsweep due to distance, I3 is the resultani-I average component of current due to distance, I4 is the increase in negative average com.. ponent of current during downsweep due to speed, and I5 is the decrease in positive average current during upsweep due to speed. The resultant average voltage across the resistor 81 is where R is the resistance of the resistor 81.

The tap of the voltage divided ||5 is adjusted to apply a positive potential of, for example, 70 volts to the lower end of the resistor 81. The purpose of this arrangement is to provide a suitable operating point for the cathode follower tube 89. This voltage is denoted hereinafter as e1. It may bevaried over a small range by means of voltage divider I|5 to provide initial adjustments of the system. The total voltage at the control grid of the tube 89, referred to ground potential, is eo-I-ei. Inasmuch as the entire load of the tube 89 is in the cathode circuit, the anode current will assume a value such that the drop in said load circuit is very slightly greater than the voltage between the control grid and ground, and as a practical matter, is substantially equal'to the grid voltage. Thus the voltage at the control grid of the relay tube 95, with respect to ground potential, is eo-t-ei.

The differential relay 91 responds to the difference between the anode currents of the relay tubes 95 and 99. If the anode current of the tube 95 is greater than that of the tube 99, the relay 91 operates in one direction while if the current of the tube 99 is greater, the relay operates in the other direction. The relay 91 may be designed so that it will remain in its mid position when the currents of the tubes 95 and 99 are equal. A voltage e2 appears at the variable tap of the voltage divider 23. This voltage is applied,

to the control grid of the tube 99. When e2 equals ei-l-eo, the control grids of the-tubes and 99 are at equal potentials. The anode currents are equal, and the armature of the relay 91 remains in tis central position, deenergizing the motor 9. The motor 9 is energized for operation in one direction when e1+e0is greater than e2, and the other direction when ei-I-eo is less than e2. Thus as long as there is any difference between ei-l-eo and ez, the motor 9 will be energized to run in the corresponding direction.

The motor 9 is mechanically coupled to one input shaft of a differential |39. The other input shaft of the differential |39 is connected to a constant speed clock motor |4I. The motor |4| is connected to the battery II through a switch |43. The output shaft I3 of the diierential |39 carries a cam |41 arranged to open the switch |43 when the shaft |45 is in a predetermined angular position. A second switch |49 similar to the switch |43 is arranged to be operated by a cam I'5I, also on the shaft I3. The cams |41 and I5| are designed so that the switch |43 remains open over a slightly greater range of rotation of the shaft I3 than the switch |49. The switch |49 is connected through a manually operable switch |53 between the grid of the relay tube 99 and ground.

The above-described arrangement of the switches |43, |49 and |53 is for the purpose of resetting of the shaft I3 to its starting position, and operates as follows:

When the shaft I3 is in any other than starting position, the switches |43 and |49 are closed by the cams |41 and 5|. If the switch |53 is now closed, the control grid of the tube 99 will be grounded, causing the tube 99 to draw considerably more current than the tube 95. The relay 91 is correspondingly actuated, causing the motor 9 to run continuously in one direction. The shaft I3 is driven thereby, through the differential |39, until the switch |43 opens, whereupon the clock motor |4| is stopped. Substantially at the same time, the switch |49 is opened by the cam I5I, restoring the control grid of the tube 99 to its original potential e2, whereupon the motor 9 is deenergized until some change occurs in the value of e0.

The shaft I3 is also coupled to the movable contact of the resistor 3, and to a pair of voltage dividers 29 and |51. An indicator I5 provided with a time dial I1 is coupled to the shaft I3 as in the systems of Figures 1 and 4.

A radio altimeter of conventional design is provided, comprising an F-M transmitter |59, a receiver III, a limiter |63, a counter |61, and a current responsive meter |69. In operation, the transmitter |59 sends a frequency modulated signal downward. The signal is reflected by the surface and received by the receiver I6 I, where it is compared with the transmitted signal to provide a beat signal having a frequency proportional to the altitude H. The beat signal is limited to a constant amplitude by the limiter I 63 and applied to the counter |61, which operates like the counter 85, with the exception that it operates continuously rather than intermittently, to provide an output current proportional to the altitude H. This current actuates the .meter |99, which may be calibrated in terms of altitude in feet.

One winding of a differential relay 21 is included in the counter output circuit, in series with the meter |59, The relay 21 is provided with a double-throw ,double-pole contact arrangement,

13 .ennnectineftne battery 33e-.|19 Vthe--.f.1r1.c i01 3.5i '.Ifhe .connections .of .the relay .ZTI and .batte1y33 and motor .3 5 ,are similar Ito =the .connections yof .the relay .-7951 .battery .II .-andmotor 9.

The motor .is coupled toa shaft AI carrying theindicator 3'I `Whichcooperates with 4the-.H/.T scaleSB asin thesystemsof Figures 1 and 4. .The 1.Shaft 4I is also coupledto the voltagedividers I9 and 2 3, and carries V,in addition a .pair of voltage dividers 3| and |55. The voltagedivider i9 corresponds to the sensitivity correction controlwof .the system of Figure 4. Similarly, the voltage divider 23 correspondsvto the intercept .bias con- .trol 23 of Figure A, and the voltage vdividers Y29 and l3:| correspond `respectively to .the voltage .controldevices 29 and 3| .ofFigure 4. The-out- .put of vthe voltage divider y3| Ais .opposed .in the differential relay .2-to that of the laltimeter, as in the system of Figure .4 to -control the motor 35. As described above, in .connection With Figure 4, the system-operates .to .position theshaft .I3 nfaocordancewith the -true 1time .from targetand the shaft 4I in 4accordance ywith the quantity fH/.T-

The vvoltagedividers .L55 and |51 are connected across the D.-C. source 9|. Their ladjustable .taps arecOnneCted to therespective .terminals of ,apolarized-relay I-'|'I. .The contacts of the relay I'I IV are connected to the bombrelease. mechanism, gnot shown. V.A Adisarmingswitch I'Ill is included. in the oircuit,and ,iscoupled .to the reset switch |53, so that when the system `is disarmed, the V.shaft is .automatically -set to its starting position.

,At the beginning of .a bombing run-toWar-.d.a .selected target, thearming switch |10 is closed, .opening the switch |53. The .time shaft .I3 Ais .at .its extreme position A.corresponding to .maxi `mum time .from target. I'heshaft 4I `conselquentlyis at .its .extreme position corresponding ltorninimum value H/T. 'The motors 9 and [el 'are both deenergized and remain so until the signalis picked up'by 'the receiving equipment, Voperating the relayl to ,close the circuit ofthe motor 9,.rotating'tlfe shaft I3 slightly away 'from its maximum position. The small initial rotav.

tion of th'e'shaft I3 closes the circuit Iof the clock Vmotor IIII which thereafter drives Ythe shaft `I3y through the-differential |39 so that the indicator lI5 moves over the scale I'I at a. rate correspond- "ing fto the passage of time. AIf the time from t'a'rgetfT as determined -by the radio equipment does not equal the time T indicated by thelin dicator I5, the relay iSTI is actuated tor-energize the motor 9. The motion of the vmotor 9 is :added 1in the `differential |39 to that of thefclock r'motor 14|, setting 'the position :of the shaft i3 :to correspond v.to thezmeasured time'from target. lf 'the `:time from target T vvas .determined by Jthe radio vdoes not remain fequal to that indifcated by the. indicator 4 5, the .motor A9 @ag-.ain 4 genergized to provide the `'proper 1correction.

long as .thenindicated time corresponds .to lthe .measured time, the `motor .Slis deenereized and thesha-ft I31is airiven only by ath-e .clock motor ilfAI 1f the frfletion signal fails, .the erelay 1.9 ',Qflens,

Afili!) rliseneaene themotor .and :the indicator Will .continue to function, although gno .corrections fwilllbemade ,until theisignal again y.comes in.

'les theftareet is faeeroahed, the Shaft laffeftates toward rits mnimum position While cthe :shaft ..Il. I.-rotate saway `from its minimiunfposition. .[lZhe :calibration of .the system is adjusted :by .means of `the .voltage ldividers .A9 and Aso that the voltages ,at .the .taps .of .the voltage dividers ,and .|51 are .egual .when Lthe .angular .posier .Vgl-, ,T

V:explained above, this is Vthe condition .at ithe instant at which release should occur. Since the :voltages at-:the movable tapsrof V.thevoltage dividers :I iand |51are equal, theresultantvoltageapplied-to the relay III is zero, causing .the contacts to close and actuate therelease mechafnism.

,Thelinvention has been described Vas an improved :radio bomb release .system wherein the slant f'distan'ce, .-slant speed, .and altitude of bomber `vvithrespect .to a target4 are substantially continuouslymeasured-by radio reflection means. Thev speed Iand Y distance information fis employed .to actuatea-.time from target shaft, and lis combined A.iirith the .altitude information toacturate-a shaft :in `faccordance lWith `:the vquantity H/YL. The gI-I/T .information Ais fed rback .into the time from targetfcomputing system to provide correction for y.the error .resulting from the measuref ment Yof 4slant speed :and distance rather than horizontal .speed .iandfdistance The positions of the T shaft vandthe H/.Tare compared to auto.- matically xrelease a bomb when the time from target :is equal to the time of fall.

.1. claimv .as Ymy invention:

.1. .A radiobombrrelease .system including, on :a .bomber craft, .radio .means for transmitting-sig;- nals to ya ,predetermined target, receiving said vsignals Iafter reflection by said target, and corn- Aparing said-transmitted and received signals for substantially continuously measuring .the slant Ydistance :and slant ,speed of said bomber craft zwith respect to said ,predetermined target, radio .altimeter rmeans .for substantially continuously -determining the .altitude -of said bomber craft, .servo means .including anoutput shaft and re.- `,sponsive .to ,the -output of said first-.mentioned radio ,means to rotate said `output shaft, further .servomeanszincluding a second output .shaft and .responsive .tothe output of saidaltimeter to rotate .said .second .output shaft, means responsive to :the positions of both of said output shafts to lbias saidaltimeten further means responsive ato the ,position Aofthe second ofvsaid outputshafts to control the distance .sensitivity of said firstmentioned Yradio means, further means responsive .to .the ,positions .of one .of .said output shafts to :biased-iid first-Inentionedradio means, and means responsive to .the 'attainment .of a Vpredetermined ,angular .relationship between said output shafts .'tojeifect .releaseof a bomb.

V2. Aradio bomb releasesystem-including radio .distance .and speedmeasuring means for substantially continuously measuring the'slant distance andsl-ant speedofra .bomhercraft with respect to 4.aspr/edeterniinedtarget,radio altimeter means. for substantially .continuously determining thealti- `=tilde of said .bomber craft, va time shaft.servo :Jneans .includingfan output shaft .coupled tofsaid irnefshaft and Responsive tothe output Vof .said .-ij-adiodistanceandspeed measuring means to-correct the l.position .of said time shaft, further-servo means including a .second output .shaft .and .responsive .tothe output .of said altimeter to rotate ,70 .Said .second output shaft, Lmeans responsive vto thepositions ofsaid second outputshaft and said time fshaft to fbias .said altimeter, V:further :means .responsive Ato fthe positions of saidsecond output shaft .and .said timeshaft .to control .the .distance .-55 sensitivity .of said radio Adistance .I speedmeadsense vuring means, further means responsive to the position of the second of said output shafts to bias said radio distance and speed measuring means, and means responsive to the attainment of a predetermined angular relationship between said second output shaft and said time shaft to effect release of a bomb.

3. A bomb release system including means for substantially continuously measuring the slant distance and slant speed of a bomber craft with 'respect to a predetermined target, means for substantially continuously determining the altitude of said bomber craft, servo means including an output shaft and responsive to the output of said rst means to rotate said output shaft, further servo means including a second output shaft and responsive to the output of said second means to rotate said second output shaft, means responsive to the positions of both of said output shafts to bias said second means, further means responsive to the positions of both of said output shafts to control the distance sensitivity of said first means, further means responsive to the position of the second of said output shafts to bias said first means, and means responsive to the attainment of a predetermined angular relationship between said output shafts to effect release of a bomb.

4. A radio bomb release system including radio means for transmitting signals from a bomber craft to a predetermined target, receiving said signals after reection by said target, and comparing said transmitted and received signals to substantially continuously measure the slant distance and slant speed of said bomber craft with respect to said predetermined target, radio altimeter means for substantially continuously determining the altitude of said bomber craft, a time shaft, means responsive to the output of said first-mentioned radio means to rotate said time shaft, means including a second shaft and responsive to the output of said altimeter to rotate said second shaft, means responsive to the positions of both of said shafts to bias said altimeter, further means responsive to the positions of both of said shafts to control the distance sensitivity of said first-mentioned radio means, further means responsive to the position of the second of said shafts to bias said first-mentioned radio means, and means responsive to the attainment of a, predetermined angular relationship between said shafts to effect release of a bomb.

5. A radio bomb release system including radio distance and speed measuring means differentially responsive to slant distance of a bomber from a selected target and slant speed of said bomber with respect to said target, servo means including an output shaft and responsive to the output of said radio means and including means responsive to the position of said output shaft for controlling the response sensitivity of said radio means to distance, whereby said output is maintained at a substantially constant value, an altimeter, further servo means including a second output shaft and responsive to the output of said altimeter and to the position of said first output `distance response sensitivity, and means responsive to the position of said second shaft to bias the output of said radio means, whereby said output approximates that which would be obtained in response to horizontal, rather than slant, distance and speed, and bomb release means responsive to the positions of both of said output shafts.

6. A radio bomb release system including radio distance and speed measuring means differentially responsive to slant distance of a bomber from a selected target and slant speed of said bomber with respect to said target, a time shaft, servo means responsive to the output of said radio means to drive said time shaft and including means responsive to the position of said time shaft for controlling the response sensitivity of said radio means to distance, whereby said output is maintained at a substantially constant value, and said time shaft rotates at substantially constant speed, an altimeter, further servo means including a second shaft and responsive to the output of said altimeter and to the position of said time shaft, means responsive to the position of said second shaft to superimpose a second control upon said first mentioned control of said distance response sensitivity, and means responsive to the position of the second of said shafts to bias the output of said radio means, whereby said output approximates that which would be obtained in response to horizontal, rather than slant, distance and speed, and bomb release means responsive to the positions of both said shafts.

'7. A radio bomb release system including radio distance and speed measuring means differentially responsive to slant distance of a bomber from a, selected target and slant speed of said bomber with respect to said target, a time shaft, clock means for driving said time shaft, servo means coupled to said time shaft and responsive to the output of said radio means to correct the position of said time shaft and including means responsive to the position of said time shaft for controlling the response sensitivity of said radio means to distance, whereby said output is maintained at a substantially constant value, an altimeter, further servo means including a second shaft and responsiveto the output of said altimeter and to the position of said time shaft, means responsive to the position of said second output shaft to superimpose a second control upon said first mentioned control of said distance response sensitivity, and means responsive to the position of said second shaft to bias the output of said radio means, whereby said output approximates that which would be obtained in response to horizontal, rather than slant, distance and speed, and bomb release means responsive to the positions of both of said shafts.

8. A bomb release system including means differentially responsive to slant distance of' a bomber from a selected target and slant speed of said bomber with respect to said target, servo means including an output shaft and responsive to the output of said first means and including means responsive to the position of said output shaft for controlling the response sensitivity of said rst means to distance, whereby said output is maintained at a substantially constant value, altimeter means, further servo means including a second output shaft and responsive to the output of said altimeter and to the position of said first output shaft, means responsive to the position of said second output shaft to superimpose a'second control upon said first mentioned control of said distance response sensitivity, and means responsive to the position of the second of said output shafts to bias the output of said first means, whereby said output approximates that which would be obtained in response to horizontal, rather thanislant, distance and speed,

175 and bomb release means responsive to the positions of both of said output shafts. 9. A radio bomb release system including radio distance and speed measuring means providing an output voltage of magnitude wherein a and li are constants, u and 1' are factors depending upon adjustments of said means, R ls the slant distance of a bomber from a selected target, S is the slant speed of said bomber with respect to said target, and pc is a bias voltage aimplied to said means, altimeter means providing an output voltage E2=nh-qmc, wherein n is a constant, h is the altitude of said bomber craft, and qmc is a bias voltage applied to said altimeter, servo means including an output shaft and responsive to the output voltage Ei to rotate said shaft, further servo means including a second output shaft and responsive to the voltag-e E2 to rotate said second output shaft, means responsive to the positions of both of said shafts to control the magnitude of said altimeter bias voltage dmc, whereby said second servo system substantially maintains said second shaft at an angular displacementifrom a predetermined reference position, directly proportional to h and inversely proportional to the displacement of said first output shaft, means responsive to the position of the second of said output shafts to control the adjustment of said radio means determining said factor u, and means responsive to the positions of both of said output shafts to control the magnitude of said bias voltage pc, whereby said output voltage E1 becomes zero upon the attainment of said first output shaft of an angular position substantially corresponding to the quotient T of the horizontal distance of said bomber from said target by the horizontal speed of said bomber with respect to' said target, and means responsive to the attainment of a predetermined angular relationship between the positions of said rst and second output shafts to release a bomb.

10. A radio bomb release system including radio distance and speed measuring means providing an output voltage of magnitude wherein a and b are constants, u and r are factors depending upon adjustments of said means, R is ,the slant distance of a bomber from a selected target, S is the slant speed of said bomber with respect to said target, and pc is a bias voltage applied to said means, altimeter means providing an output voltage Ez=nh-qmc, wherein 11, is a constant, h is the altitude of said bomber craft, and qmc is a ias voltage applied to said altimeter, a time shaft, clock means for driving said time shaft, servo means coupled to said shaft and responsive to the output voltage E1 to correct the position of said shaft, further servo means including a second shaft and responsive to the voltage E2 to rotate said second shaft, means responsive to the positions of both of said shafts to control the magnitude of said altimeter bias voltage qmc, whereby said second servo system substantially maintains said second shaft 'at an angular displacement, from a predetermined reference position, directly proportional to h and inversely proportional to the displacement of said time shaft, means responsive to the position of said second output shaft to control the adjustment of said radio means determining said factor u, and means responsive to the positions of both of said shafts to control the magnitude of said bias voltage qmc, whereby said output voltage E1 becomes zero upon the attainment by said time shaft of an angular position substantially corresponding to the quotient T of the horizontal distance of said bomber from said target by the horizontal speed of said bomber with respect to said target, and means responsive to the attainment of a predetermined angular relationship between the positions of said r-st and second shafts to release a bomb.

11. A bomb release system including means providing an output voltage of magnitude wherein a and b are constants, u and r are factors depending upon adjustments of said means, R is the slant distance of a bomber from a selected target, S is the slant speed of said bomber with respect to said target, and pc i-s a bias voltage applied to said means, altimeter means providing an output voltage E2=nh-qmc, wherein n is a constant, h is the altitude of said bomber craft, and qmc i-s a bias voltage applied to said altimeter, servo means including an output shaft and responsive to the output voltage E1 to rotate said shaft, further servo means including a second output shaft and responsive to the voltage E2 to rotate said second output shaft, means responsive to the positions of both of said shafts to control the magnitude of said altimeter bias voltage qmc, whereby said second servo system substantially maintains said second shaft at an angular displacement, from a predetermined reference position, directly proportional to h and inversely proportional to the displacement of said first output shaft, means responsive to the position of said second output shaft to control the adjustment of said first mentioned means determining 4said factor u, and means responsive to the positions of both of said output shafts to control the magnitude of said bias voltage pc, whereby said output voltage E1 becomes zero upon the attainment of said first output shaft of an angular position substantially corresponding to the quotient T of the horizontal distance of said bomber from said target by the horizontal speed of said bomber with respect to said target, and means responsive to the attainment of a predetermined angular relationship between the positions of said first and second output shafts to release a bomb.

12. A bomb release system including means providing an output voltage of magnitude wherein a and b are constants, u and r factors depending upon adjustments of said means, R is the slant distance of a bomber from a selected target, S is the slant speed of said bomber with respect to said target, and pc is a bias voltage applied to said means, altimeter means providing an output voltage E2=nh-qmc, wherein n is a constant, h is the altitude of said bomber craft, and qmc is a bias voltage applied to said altimeter, a time shaft, clock means for driving said time shaft, servo means coupled to said time shaft and responsive to the output voltage E1 to correct the position of said shaft, further servo means including a, second shaft and responsive to the voltage E2 to rotate said second shaft, means responsive to the positions of both of said shafts to control the magnitude of said altimeter bias voltage qmc, whereby said second servo system substantially maintains said second' 19 shaft at an vangular displacement, from a predetermined reference position, directly proportional to h and inversely proportional to the displacement of said time shaft, means responsive to the position of said second shaft to control the adjustment of said rst mentioned means determining said factor u, and means responsive to the positions of both of said shafts to control the magnitude of said bias voltage pc, whereby said output voltage E1 becomes zero upon the attainment of said time shaft of an angular position substantially corresponding to the quotient T of the horizontal distance of said bomber from said target by the horizontal speed of said bomber with respect to said target, and means responsive to the attainment of'a predetermined angular relationship between the positions of saidvrst and second shafts to release a bomb.

13. The method of controlling the release of a bomb from a mobile craft to strike a selected target, comprising the steps of substantially continuously measuring the slant distance and slant speed of said craft with respect to said target, substantially continuously determining the altitude of said craft, deriving approximate time from target information from said slant speed and slant distance information, correcting said approximate time from target information in response to both said altitude and said time from targetl information, and effecting bomb release upon the attainment of a predetermined relationship between said altitude and said corrected time from target.

14. The method of controlling the release of a bomb' from a mobile craft so as to strike a selected target, comprising the steps of providing a continuous indication of the passage of time, measuring thev slant distance and slant speed of said craft with respect to said target to provide approximate time from target information, measuring the altitude of said craft, correcting said approximate time from target information in accordance with a predetermined function of said altitude, adjusting said time indication in accordance with said corrected time from target information, and effecting bomb release in response to the occurrence of a predetermined relationship between said altitude and said indicated time from target.

DAVID G. C. LUCK. 

